Excessive attraction detection device

An excessive attraction detection device capable of detecting that an excessive amount of workpieces is attracted and retained by a workpiece attraction device,

• wherein the excessive attraction detection device comprises a cylinder member including a piston and a magnetic part including a permanent magnet used for attraction, the permanent magnet used for attraction is displaceable integrally with the piston between an attracted position and a retracted position, and a sensor is provided to detect a position of the permanent magnet used for attraction;
• and
• an attracted position release biasing force, which acts on the piston in order to bias the permanent magnet used for attraction from the attracted position toward the retracted position, is set to a value that is larger than a mutually attractive magnetic force of one of the workpieces and the permanent magnet used for attraction at the attracted position in a case that the one of the workpieces is attracted and retained by the workpiece attraction device, and that is smaller than a mutually attractive magnetic force of the workpieces and the permanent magnet used for attraction at the attracted position in a case that two of the workpieces are attracted and retained by the workpiece attraction device.